In this paper, we consider "sinus-lifting motion" which is an effective motion of a snake for rapid movement. In this motion, a snake lifts up some parts of its body from the ground, and switches the lifted parts dynamically. This motion is analyzed based on a dynamic model of an n-link snake robot. We introduce the energy efficiency as a cost function to generate motion of a snake robot. We propose a control strategy for switching grounded parts of the snake robot so as to minimize the energy consumption. Simulation results show that the motion that optimizes the energy efficiency of the snake robot differs depending on the velocity to be generated and the optimal motion is similar to the sinus-lifting motion.